Recent years have witnessed practical use of a flat-panel display in various products and fields. This has led to a demand for a flat-panel display that is larger in size, achieves higher image quality, and consumes less power.
Under such circumstances, great attention has been drawn to an organic EL display device that (i) includes an organic EL element which uses electroluminescence (hereinafter abbreviated to “EL”) of an organic material and that (ii) is an all-solid-state flat-panel display which is excellent in, for example, low-voltage driving, high-speed response, and self-emitting characteristics.
An organic EL display device includes, for example, (i) a substrate made up of members such as a glass substrate and TFTs (thin film transistors) provided to the glass substrate and (ii) organic EL elements provided on the substrate and connected to the TFTs.
An organic EL element is a light-emitting element capable of high-luminance light emission based on low-voltage direct-current driving, and includes in its structure a first electrode, an organic EL layer, and a second electrode stacked on top of one another in that order, the first electrode being connected to a TFT.
The organic EL layer between the first electrode and the second electrode is an organic layer including a stack of layers such as a hole injection layer, a hole transfer layer, an electron blocking layer, a luminescent layer, a hole blocking layer, an electron transfer layer, and an electron injection layer.
A full-color organic EL display device typically includes, as sub-pixels aligned on a substrate, organic EL elements of red (R), green (G), and blue (B). The full-color organic EL display device carries out an image display by, with use of TFTs, selectively causing the organic EL elements to each emit light with a desired luminance.
The organic EL elements in a light-emitting section of such an organic EL display device is generally formed by multilayer vapor deposition of organic films. In production of an organic EL display device, it is necessary to form, for each organic EL element that is a light-emitting element, at least a luminescent layer of a predetermined pattern made of an organic luminescent material which emits light of the colors.
In formation of films in a predetermined pattern by multilayer vapor deposition, a method such as a vapor deposition method that uses a mask referred to as a shadow mask, an inkjet method or a laser transfer method is applicable. Among these methods, the vapor deposition method that uses a mask referred to as a shadow mask is the most common method.
In a vapor deposition method employing a mask called a shadow mask, a vapor deposition source that evaporates or sublimates a vapor deposition material is provided in a chamber inside which a reduced-pressure condition can be maintained. Then, for example, under a high-vacuum condition, the vapor deposition source is heated, and thereby the vapor deposition material is evaporated or sublimated.
Thus evaporated or sublimated vapor deposition material is vapor-deposited, as vapor deposition particles, onto a film formation target substrate onto which a film is to be formed. This vapor deposition is carried out through apertures provided to the mask for vapor deposition, so that a desired film pattern is formed.
Patent Literature 1 discloses a material supplying device as a vapor deposition particle injection device, according to one example of vapor deposition methods each employing a mask called a shadow mask as described above. This material supplying device controls an amount of the vapor deposition material from the vapor deposition source which vapor deposition material has been evaporated or sublimated, and thereby stabilizes a speed of film formation of a vapor-deposited film.
FIG. 18 is a cross sectional view schematically illustrating the material supplying device as disclosed in Patent Literature 1.
As illustrated in FIG. 18, a material supplying device 300 as described in Patent Literature 1 is configured to include (i) a gas generating chamber 301 that heats up a vapor deposition material to a first temperature so as to evaporate or sublimate the vapor deposition material and that thereby converts the vapor deposition material into a gaseous material, (ii) a temperature adjustment chamber 302 that controls a temperature of the gaseous material, and (iii) a piping section 303 that connects the gas generating chamber 301 and the temperature adjustment chamber 302.
Further, in the vicinity of an exit of the temperature adjustment chamber 302, a slit section 304 is provided. This slit section 304 serves as a mask for vapor deposition. This configuration allows the gaseous material to be vapor-deposited onto the film formation target substrate 200 through the slit section 304.
On an upstream side in the temperature adjustment chamber 302 with respect to the slit section 304 (i.e. on a side of the temperature adjustment chamber 302 on which side the temperature adjustment chamber 302 is connected to the piping section 303), a first heater 305 is provided. This first heater 305 lowers the temperature of the vapor deposition material (gaseous material) that has been evaporated or sublimated, to a second temperature that is lower than the first temperature.
The temperature adjustment chamber 302 is provided with a plurality of multi-hole plates 306. Each of the plurality of multi-hole plates 306 is provided with a plurality of apertures 306a through which the gaseous material passes. When the gaseous material comes in contact with a multi-hole plate 306, heat exchange occurs. As a result, the temperature of the gaseous material is controlled so as to be at the second temperature.
Further, at the slit section 304 and on a downstream side with respect to the slit section 304 in the temperature adjustment chamber 302, a second heater 307 is provided. The second heater 307 raises the temperature of the gaseous material to a third temperature that is higher than the second temperature on the upstream side with respect to the slit section 304.
In Patent Literature 1, the material (gaseous material) that has been evaporated or sublimated is saturated by setting the temperature of the material to the second temperature that is lower than the first temperature in the temperature adjustment chamber 302 so that the material is at a saturated vapor pressure. This prevents a supply amount of the gaseous material from varying depending on a change in temperature. Meanwhile, at the slit section 304 and on the downstream side with respect to the slit section 304, the gaseous material is heated to the third temperature that is higher than the second temperature so that the gaseous material is prevented from solidifying.
More specifically, in Patent Literature 1, as the vapor deposition material, Alq3 (aluminum quinolinol complex, aluminato-tris-8-hydroxyquinolate) is used as a host material of a luminescent layer. Further, the first temperature is set in a range of 350° C. to 400° C., the second temperature is set in a range of 300° C. to 350° C., and the third temperature is set in a range of 350° C. to 400° C.